The pipiwai trail hike is located in the Haleakala National Park at Oheo Gulch. Pipiwai Trail is 4 miles roundtrip, gaining 650-feet in elevation. It takes 2 1/2 – 5 hours to hike, depending on your the physical condition. Waimoku Falls are final destination of hike, falling 400-feet down a sheer lava rock wall shaped like a horse shoe.